In order to maintain the integrity of a stack of boxes or other more or less similar goods during transportation and handling, it is convenient to enshroud the stack in an envelope of thermally shrinkable plastic sheet material--usually polyethylene--which is then subjected to a heat treatment in order to form a substantially solid package. When the stack is supported on a pallet, as is frequently the case, the envelope may be a hood held down around the stack and the pallet so as to embrace the latter with its contracting rim.
Boxes and other stackable goods, e.g. bottles placed between sheets of cardboard, are often provided with individual wrappings of thermoplastic foils having a tendency to adhere to the surrounding envelope during the shrinking process. Such a fusion creates difficulties when the goods are to be unstacked and removed from the pallet.
Various solutions to this problem have already been proposed. One of them involves the use of polyvinylchloride (PVC) for the individual wrappings, yet this material is relatively expensive. The use of heavier wrappings of, say, polyethylene (PE) to prevent them from tearing because of local adhesions is also costly. Separating the shrinkable envelope from the goods by a sheath of nonadhering foil requires an additional operating step, namely that of placing the sheath around the stack. This step can be avoided through the use of multilayer envelopes with an outer layer of PE and an inner layer of nonbonding character. However, such envelopes are more costly to produce and their adhesion-preventing inner layer--having a higher melting point than PE--contracts less readily and thus retards the shrinking process.